The present invention relates generally to an improved front suspension system for a snowmobile, and more specifically to a suspension system connecting skis to the chassis of a snowmobile in such a manner that lateral movement of the skis relative to the chassis during deflection of the suspension system is substantially eliminated.
Snowmobiling has changed dramatically during the last decade and more sophisticated approaches to old problems are needed. One problem that has been around for a long time and which has become more of a concern now that more of the new snowmobiles are capable of speeds over 100 mph is the quick lateral movements of the snowmobile which are induced by the front suspension reacting to undulations in the terrain. At high speed this can be a very disconcerting feeling for a rider or passenger and may be accentuated by conditions such as when bumps are encountered during the traversing of a hillside at high speed.
Snowmobiles are generally designed to have either a single rider or two riders with one rider sitting in front of the other rider and driving the snowmobile. The driver is usually an active participant and is reacting to the terrain along with the snowmobile where, however, the rider is usually unable to see the trail as clearly as the driver and often times is surprised by quick lateral movements of the snowmobile. Riding at night or in conditions in which visibility is limited may also result in the driver being surprised by an imperfection in the trail and the suspension causing a quick lateral movement. The instant invention approaches this problem and eliminates undesirable lateral shifting of the snowmobile induced by a front suspension geometry that laterally shifts the skis relative to the chassis during suspension travel, thereby providing a more comfortable and safer ride.
Prior to the instant invention, the prior art has taken a number of different approaches to snowmobile front suspensions. One approach, depicted in U.S. Pat. No. 4,489,954, shows a strut-type suspension for controlling movement of a ski relative to the chassis. This type of system has found extensive usage in automobiles, but some shortcomings have become apparent when it is used on a snowmobile because of the rough terrain and severe conditions in which snowmobiles are often used. One problem being the cost of replacement struts when they are damaged.
Some prior art types of suspension systems have not recognized the problem or at least not openly dealt with the problem. One typical prior art suspension includes a leaf-type spring attached to a ski and to a steering spindle near its midpoint, such an arrangement is depicted in U.S. Pat. No. 3,920,091. Another prior art suspension system, depicted in U.S. Pat. No. 3,140,752, shows a pair of equal length arms 3 and 4 forming a parallelogramic linkage for supporting skis laterally disposed relative to a chassis. The skis in this arrangement follow an arc during deflection of the suspension. Yet another prior art suspension system, depicted in U.S. Pat. No. 3,884,314, shows an upper suspension bracket 46 and a lower suspension member 58 supporting a spindle 36 which in turn is attached to a ski 16. Some of the suspension components of this arrangement have very basic similarities to the instant invention. However, this arrangement fails to teach the concept or show the end result of the present invention. U.S. Pat. No. 4,082,155 shows a wheeled undercarriage for a snowmobile which includes a pair of suspension members 92 and 96 which are attached to a support bracket 100 by upper and lower ball joints 102 and 104. Bracket 100 of this device has a horizontally extending spindle to which a wheel assembly is attached. Finally, a prior art device, shown in U.S. Pat. No. 4,671,521, includes a control arm 34 cooperating with upper and lower suspension arms 36 and 37, respectively, for controlling movement of spindle 18 relative to the snowmobile chassis.
No where in any of the prior art devices is there found any teaching of an improved front suspension system as taught by the instant invention.